Picosecond photoemission sampling for contactless high speed integrated circuit diagnostics

Abstract

The idea of utilizing time-resolved photoemission for contactless electrical testing on internal nodes of IC's is rather young. Initial studies quickly showed the advantages the technique offers over other methods. After a short review of the basic principle and its attractive features, this paper reports on the progress made toward meeting the requirements for IC testing and diagnostic equipment. The goals of IC testing are to provide high time and voltage resolutions with short testing time, and simultaneously high spatial resolution independent of the circuit technology (Si, GaAs). Here, the emphasis is on the time and voltage resolutions and short testing time. In the photoemission process, these parameters are independent of the spatial resolution in the regime of interest. The investigation is carried out with a pulsed-laser system generating picosecond pulses in the UV range. The measurements presented were performed on a photoconductive switch. This allows testing the time resolution of the method by ultra-fast signals and generating the electric transients to be sampled by the same laser source as the sampling pulse. The latter point guarantees almost jitter-free operation. The results clearly demonstrate that photoemission sampling is capable of contactless diagnostics and testing of very high-speed circuits with a high voltage resolution and short testing time.